U.S. patent application number 16/304070 was filed with the patent office on 2020-02-27 for package-integrated piezoelectric device for blood-pressure monitoring using wearable package systems.
The applicant listed for this patent is Intel Corporation. Invention is credited to Aleksandar ALEKSOV, Feras EID, Adel ELSHERBINI, Sasha N. OSTER, Johanna M. SWAN.
Application Number | 20200060558 16/304070 |
Document ID | / |
Family ID | 60912997 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200060558 |
Kind Code |
A1 |
ALEKSOV; Aleksandar ; et
al. |
February 27, 2020 |
PACKAGE-INTEGRATED PIEZOELECTRIC DEVICE FOR BLOOD-PRESSURE
MONITORING USING WEARABLE PACKAGE SYSTEMS
Abstract
Embodiments of the invention include a wearable blood-pressure
monitor and methods of forming such devices. In an embodiment, the
blood-pressure monitor includes a stretchable substrate.
Additionally, a semiconductor die may be embedded within the
stretchable substrate. In order to determine blood-pressure, the
blood-pressure monitor may include an electrocardiogram sensor and
a piezoelectric sensor for detecting a ballistocardiograph
response. In an embodiment, both types of sensor may be
electrically coupled to the semiconductor die. Embodiments of the
invention include a piezoelectric sensor that includes a
piezoelectric layer and a first and second electrode. In an
embodiment the first electrode is in contact with a first surface
of the piezoelectric layer, and the second electrode is in contact
with a second surface of the piezoelectric layer that is opposite
to the first surface.
Inventors: |
ALEKSOV; Aleksandar;
(Chandler, AZ) ; EID; Feras; (Chandler, AZ)
; OSTER; Sasha N.; (Chandler, AZ) ; ELSHERBINI;
Adel; (Chandler, AZ) ; SWAN; Johanna M.;
(Scottsdale, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Intel Corporation |
Santa Clara |
|
CA |
|
|
Family ID: |
60912997 |
Appl. No.: |
16/304070 |
Filed: |
July 2, 2016 |
PCT Filed: |
July 2, 2016 |
PCT NO: |
PCT/US2016/040905 |
371 Date: |
November 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2562/164 20130101;
A61B 5/02141 20130101; A61B 5/021 20130101; H01L 41/1876 20130101;
A61B 2562/0215 20170801; A61B 5/04085 20130101; H01L 41/1871
20130101; A61B 5/1102 20130101; H01L 41/1873 20130101; A61B 5/7278
20130101; H01L 41/316 20130101; H01L 41/0805 20130101; H01L 41/317
20130101; A61B 2562/0247 20130101; A61B 5/6833 20130101; A61B
2562/125 20130101 |
International
Class: |
A61B 5/021 20060101
A61B005/021; A61B 5/0408 20060101 A61B005/0408; A61B 5/00 20060101
A61B005/00; A61B 5/11 20060101 A61B005/11; H01L 41/08 20060101
H01L041/08; H01L 41/316 20060101 H01L041/316; H01L 41/317 20060101
H01L041/317 |
Claims
1. A wearable device, comprising: a piezoelectric sensor embedded
within a stretchable substrate, wherein the piezoelectric sensor
comprises: a piezoelectric layer; a first electrode formed in
contact with a first surface of the piezoelectric layer; and a
second electrode formed in contact with a second surface of the
piezoelectric layer that is opposite to the first surface.
2. The wearable device of claim 1, wherein the wearable device
comprises a rigid portion and a stretchable portion.
3. The wearable device of claim 2, wherein the rigid portion
comprises a semiconductor die, and wherein the stretchable portion
comprises meandering traces.
4. The wearable device of claim 3, wherein the piezoelectric sensor
is formed in the rigid portion, and wherein the piezoelectric
sensor is formed within the footprint of the semiconductor die.
5. The wearable device of claim 3, wherein the piezoelectric sensor
is formed in the stretchable portion.
6. The wearable device of claim 5, wherein the piezoelectric sensor
is electrically coupled to the semiconductor die by one or more
meandering traces.
7. The wearable device of claim 5, further comprising a stiffening
mass formed above the piezoelectric sensor.
8. The wearable device of claim 5, further comprising a plurality
of piezoelectric sensors formed in the stretchable portion.
9. The wearable device of claim 8, wherein the plurality of
piezoelectric sensors are electrically coupled to each other by
meandering traces.
10. The wearable device of claim 8, wherein the plurality of
piezoelectric sensors are arranged in a pattern similar to the
shape of a blood vessel.
11. The wearable device of claim 8, further comprising one or more
stiffening masses formed above the plurality of piezoelectric
sensors.
12. The wearable device of claim 1, further comprising an
electrocardiogram sensor.
13. The wearable device of claim 12, wherein the semiconductor die
is configured to receive signals from the electrocardiogram sensor
and the piezoelectric sensor and generate a blood-pressure
measurement.
14. The wearable device of claim 13, wherein the blood-pressure
measurement is an absolute blood-pressure measurement.
15. A method of forming a piezoelectric sensor in a wearable
device, comprising: forming a first electrode on a carrier
substrate; forming a piezoelectric layer on the first electrode;
forming a second electrode over the piezoelectric layer; forming a
stretchable substrate over the carrier substrate, wherein the
stretchable substrate encases the first electrode, the
piezoelectric layer, and the second electrode; and removing the
stretchable substrate from the carrier substrate.
16. The method of claim 15, wherein forming the piezoelectric
layer, comprises: depositing the piezoelectric layer over the first
electrode, wherein the piezo-electric layer is an amorphous layer;
and crystallizing the piezoelectric layer with a pulsed laser
anneal.
17. The method of claim 16, wherein the piezoelectric layer is
deposited with a sputtering or ink-jetting process.
18. The method of claim 16, wherein the pulsed laser anneal is
performed with an Excimer laser with an energy density in the range
of approximately 10-100 mJ/cm.sup.2 and pulse width in the range of
approximately 10-50 nanoseconds.
19. The method of claim 15, wherein the piezoelectric layer is lead
zirconate titanate (PZT), potassium sodium niobate (KNN), or zinc
oxide (ZnO).
20. The method of claim 15, wherein a plurality of wearable devices
are formed on a single carrier substrate.
21. A wearable blood-pressure monitor, comprising: a stretchable
substrate; a semiconductor die embedded in the stretchable
substrate; an electrocardiogram sensor electrically coupled to the
semiconductor die; and a ballistocardiograph sensor embedded within
the stretchable substrate and electrically coupled to the
semiconductor die, wherein the ballistocardiograph sensor is a
piezoelectric sensor that comprises: a piezoelectric layer; a first
electrode formed in contact with a first surface of the
piezoelectric layer; and a second electrode formed in contact with
a second surface of the piezoelectric layer that is opposite to the
first surface.
22. The wearable blood-pressure monitor of claim 21, wherein the
semiconductor die is configured to receive signals from the
electrocardiogram sensor and the ballistocardiograph sensor and
generate a blood-pressure measurement.
23. The wearable blood-pressure monitor of claim 21, wherein the
piezoelectric sensor is formed within the footprint of the
semiconductor die.
24. The wearable blood-pressure monitor of claim 21, wherein the
piezoelectric sensor is not formed within the footprint of the
semiconductor die, and wherein the piezoelectric sensor is coupled
to the semiconductor die by one or more meandering traces.
25. The wearable blood-pressure monitor of claim 24, further
comprising a plurality of piezoelectric sensors, wherein the
plurality of piezoelectric sensors are electrically coupled to each
other by meandering traces, and wherein the plurality of
piezoelectric sensors are arranged in a pattern similar to the
shape of a blood vessel.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the present invention relate generally to the
manufacture of wearable systems for monitoring blood-pressure and
methods of forming such systems. In particular, embodiments of the
present invention relate to the use of piezoelectric sensors for
monitoring the heart and methods for manufacturing such
devices.
BACKGROUND OF THE INVENTION
[0002] Mobile blood-pressure monitoring (BPM) systems have proven
to be a difficult product to successfully manufacture and market.
Currently there is no commercially available/viable solution to
provide continuous mobile BPM. Instead, currently available BPM
systems rely on an inflatable cuff. Such systems require a large
battery that is used to periodically inflate and deflate the cuff.
Accordingly, this solution is bulky and only allows for
measurements at discrete times. Such systems are truly only
desirable for people with known blood-pressure problems (high or
low) as a healthy person who is not suspected to have any
heart/vascular problem would not desire to voluntarily use such a
bulky device, especially not on a daily basis or for a prolonged
period of time.
[0003] However, there are solutions to provide BPM other than
inflatable cuffs. Essentially, these solutions require a
combination of at least two of the three methods to measure heart
rate (i.e., electrocardiography (ECG), ballistocardiography (BCG)
and photoplethysmography (PPG)). One such BPM system utilizes a
combination of ECG and PPG. There are, however, significant
drawbacks to these types of systems as well. Particularly, the use
of PPG sensors requires a substantial power budget, because PPG
sensors rely on reflection of light from under the skin that is
shone by a relatively high power light emitting diode (LED). The
power budget of the LED alone can easily surpass the power budget
of the rest of the electronic system including low power CPU,
ASICs, ECG, motion sensors and Bluetooth Low Energy (BTLE). For
example, the power budget of a system (without the LED) may be
approximately 45 mW, while a PPG enabled sensor module alone may
have a power budget of approximately 50 mW. As such, PPG systems
suffer from short battery life or, alternatively, they are bulky
due to larger batteries.
[0004] Some alternative systems have been proposed that include a
combination of BCG and ECG. However these systems suffer from low
processing volumes and large form factors (in the X, Y, and Z
dimensions). Such systems utilize a discrete piezoelectric patch
and attempt to manufacture or assemble the other components
(flexible circuit, electrodes, etc.) on top of the discrete
piezoelectric patch. Accordingly, the wearability of the system is
decreased because the piezoelectric patch limits the flexibility.
Additionally, the need to use discrete components increases
manufacturing costs and results in relatively large form
factors.
[0005] Finally, some systems have proposed the combination of PPG
and BCG sensors. However, this combination fails to provide a
useful device because of the drawbacks from both PPG and BCG.
Particularly, the PPG sensor requires a high power budget and the
BCG sensor has poor form factor and is not flexible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A is a cross-sectional illustration of a wearable
system that includes a piezoelectric sensor embedded below a die,
according to an embodiment of the invention.
[0007] FIG. 1B is a plan view illustration of a portion of the
wearable system that more clearly illustrates the meandering
traces, according to an embodiment of the invention.
[0008] FIG. 2A is a cross-sectional illustration of a wearable
system that includes a piezoelectric sensor that is not formed
within the footprint of a die, according to an embodiment of the
invention.
[0009] FIG. 2B is a cross-sectional illustration of a wearable
system that includes a piezoelectric sensor that is formed below a
stiffening mass, according to an embodiment of the invention.
[0010] FIG. 3A is a cross-sectional illustration of a wearable
system that includes a plurality of piezoelectric sensors,
according to an embodiment of the invention.
[0011] FIG. 3B is a plan view illustration of a portion of the
wearable system that more clearly illustrates the meandering traces
that electrically couple the plurality of piezoelectric sensors,
according to an embodiment of the invention.
[0012] FIG. 4A is a cross-sectional illustration of the wearable
system after a processing operation for forming the first electrode
of the piezoelectric sensor has been performed, according to an
embodiment of the invention.
[0013] FIG. 4B is a cross-sectional illustration of the wearable
system after a processing operation for forming the piezoelectric
layer has been performed, according to an embodiment of the
invention.
[0014] FIG. 4C is a cross-sectional illustration of the wearable
system after a processing operation for forming a dielectric layer
has been performed, according to an embodiment of the
invention.
[0015] FIG. 4D is a cross-sectional illustration of the wearable
system after a processing operation for forming a seed layer has
been performed, according to an embodiment of the invention.
[0016] FIG. 4E is a cross-sectional illustration of the wearable
system after processing operations for forming and patterning a
resist layer have been performed, according to an embodiment of the
invention.
[0017] FIG. 4F is a cross-sectional illustration of the wearable
system after a processing operation for forming the second
electrode has been performed, according to an embodiment of the
invention.
[0018] FIG. 4G is a cross-sectional illustration of the wearable
system after processing operations for removing the resist layer
and the remaining portions of the seed layer have been performed,
according to an embodiment of the invention.
[0019] FIG. 4H is a cross-sectional illustration of the wearable
system after processing operations for forming subsequent metal
layers, integrating a semiconductor die, and forming the
stretchable substrate have been performed, according to an
embodiment of the invention.
[0020] FIG. 4I is a cross-sectional illustration of the wearable
system after a processing operation for removing the carrier
substrate has been performed, according to an embodiment of the
invention.
[0021] FIG. 5 is a schematic of a computing device built in
accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Described herein are systems that include piezoelectric
sensors for use in mobile BPM and methods of forming such devices.
In the following description, various aspects of the illustrative
implementations will be described using terms commonly employed by
those skilled in the art to convey the substance of their work to
others skilled in the art. However, it will be apparent to those
skilled in the art that the present invention may be practiced with
only some of the described aspects. For purposes of explanation,
specific numbers, materials and configurations are set forth in
order to provide a thorough understanding of the illustrative
implementations. However, it will be apparent to one skilled in the
art that the present invention may be practiced without the
specific details. In other instances, well-known features are
omitted or simplified in order not to obscure the illustrative
implementations.
[0023] Various operations will be described as multiple discrete
operations, in turn, in a manner that is most helpful in
understanding the present invention, however, the order of
description should not be construed to imply that these operations
are necessarily order dependent. In particular, these operations
need not be performed in the order of presentation.
[0024] Embodiments of the present invention enable mobile and
continuous BPM by combining ECG and BCG signals. In contrast to the
discrete BCG sensors described above, embodiments of the present
invention utilize BCG sensors that include a piezoelectric element
that is built directly into the package by integrating the process
flow for creating piezoelectric layers into a wearable/stretchable
substrate. Accordingly, embodiments of the invention allow for the
fabrication of a BCG module that is highly conformal to the human
body and does not significantly increase the form factor of the
system. In addition to being more comfortable to wear due to the
high level of conformability, flexible packages also provide a more
accurate BCG signal since the contact between the skin and the
sensor is improved.
[0025] Furthermore, embodiments of the invention are able to
utilize the power-efficient nature of a piezoelectric sensor to
minimize the power budget of the system. Since embodiments of the
invention rely on an external mechanical source to compress the
piezoelectric layer (i.e., the ballistic response of the heart
provides an acoustic wave that compresses the piezoelectric layer),
the power budget for the system is minimal. Additionally, in some
embodiments, the ECG sensor may only be activated at discrete times
(e.g., at regular intervals, or when the BCG sensor detects an
anomaly in the heart rate). In such embodiments, selectively
turning on the ECG sensor may further reduce the power budget of
the system.
[0026] Another beneficial aspect of embodiments of the invention is
the reduction of fabrication costs. Instead of relying on discrete
components that are processed further, embodiments of the present
invention may allow for high volume manufacturing. For example,
embodiments of the invention include methods for fabricating the
piezoelectric layers of the BCG sensor as part of the substrate
itself at the panel level (e.g., 0.5 m.times.0.5 m panels).
Accordingly, each panel may contain hundreds of BPM systems that
are processed in parallel, thereby significantly reducing the cost
of the systems.
[0027] Referring now to FIG. 1A, a cross-sectional illustration of
a wearable system 100 is illustrated, according to an embodiment of
the invention. As illustrated, the wearable system 100 is formed on
a stretchable substrate 110. The stretchable substrate 110 is a
compliant material that allows for the wearable system 100 to
stretch, flex, bend, twist, etc. The compliant nature of the
stretchable substrate 110 may be attributable to a low modulus. For
example, the elastic modulus of the stretchable substrate 110 may
be less than approximately 10 MPa. In an exemplary embodiment, the
elastic modulus of the stretchable substrate 110 may be between
approximately 100 kPa and 10 MPa. By way of example, the
stretchable substrate 110 may be polydimethylsiloxane (PDMS) or
polyurethane.
[0028] The wearable system 100 may include one or more stretchable
portions 111 and one or more rigid portions 112. According to an
embodiment, the stretchable portions 111 include meandering traces
122 that provide electrical connections between components of the
wearable system 100, and the rigid portions 112 include one or more
semiconductor dice 160. In the illustrated embodiment, the wearable
system 100 includes two rigid portions 112. According to an
embodiment, each rigid portion 112 may include one or more
semiconductor dice 160, however embodiments are not limited to such
configurations. For example, more than two semiconductor dice 160
may be included in each rigid portion 112. In an embodiment, the
semiconductor die 160 includes one or more electrical devices (not
shown). For example, the electrical devices may include one or more
of a processor, a memory component, a sensor, a
microelectromechanical system (MEMS), or the like, or any
combination thereof. In an embodiment the semiconductor die 160 may
be a system-on-a-chip (SoC).
[0029] According to an embodiment, a modulus of the semiconductor
die 160 may be greater than a modulus of the stretchable substrate
110. For example, the elastic modulus of the semiconductor die 160
may be greater than approximately 100 GPa. In an embodiment, the
elastic modulus of the semiconductor die 160 may be between
approximately 100 GPa and 120 GPa. Accordingly, the greater modulus
of the semiconductor die 160 reduces the overall compliance of the
rigid portions 112, thereby causing the stretching of the wearable
device 100 to be primarily located in the stretchable portions
111.
[0030] According to an embodiment, the semiconductor die 160 is a
flip-chip semiconductor die. The flip-chip structure of the
semiconductor dice 160 may be substantially similar to those
presently known in the art. For example, the back end of line
interconnect stack 162 of the die 160 may be electrically coupled
to vias 142 and pads 140 formed in/on one or more dielectric layers
144. In an embodiment, an underfill material 164 may also be used
between the die 160 and the dielectric layers 144. According to an
embodiment, the pads 140 and vias 142 may include a conductive
stack of materials, such as, but not limited to adhesion promoters,
seed layers, copper, silver, gold, or alloys thereof, and oxidation
inhibitors. While a flip-chip die 160 is illustrated in FIG. 1A, it
is to be appreciated that the semiconductor die 160 is not limited
to flip-chip bonding, and other interconnect structures, such as a
wire-bonding, are also within the scope of embodiments of the
invention.
[0031] According to an embodiment, the interconnect lines 122 in
the stretchable portion 111 are formed in a meandering pattern in
order to allow for the interconnect lines 122 to stretch as the
wearable device 100 is stretched. In an embodiment, the
interconnect lines 122 may be covered by a dielectric layer 124.
The cross-sectional illustration in FIG. 1A illustrates a plurality
of portions of a single interconnect line 122. In order to more
clearly illustrate the meandering pattern, a plan view of
stretchable portion 111 is illustrated in FIG. 1B. As illustrated,
the meandering pattern is a repetitive switchback pattern, though
other meandering patterns that allow for the interconnect lines 122
to stretch as the wearable device 100 is stretched may also be
used. In FIG. 1B, the interconnect line 122 is hidden by the
dielectric layer 124, and is therefore represented with dashed
lines to indicate that the interconnect line 122 is formed below
the dielectric layer 124.
[0032] Embodiments of the invention include a meandering pattern
that allows for the interconnect lines 122 to stretch approximately
40% or greater without failing (i.e., the length of the fully
stretched interconnect lines 124 along the stretched dimension may
be approximately 40% longer than the un-stretched length of the
interconnect lines 124). Additional embodiments include a
meandering pattern that allows for the interconnect lines 124 to
stretch between approximately 45% and 55% without failing. The
interconnect lines 124 may be any commonly used conductive material
for interconnect lines. For example, the interconnect lines 122 may
be copper, silver, gold, or alloys thereof. Additional embodiments
may further include interconnect lines 122 that are a conductive
stack of materials, such as, but not limited to adhesion promoters,
seed layers, and oxidation inhibitors.
[0033] Referring back to FIG. 1A, the illustrated embodiment
includes a piezoelectric sensor 150 that is formed in one of the
rigid portions 112. For example, the piezoelectric sensor 150 may
be formed substantially within the footprint of a die 160. In the
illustrated embodiment, the piezoelectric sensor 150 is integrated
into the dielectric layers 144 below the die 160. The piezoelectric
sensor 150 may include a piezoelectric layer 156. In an embodiment,
a first electrode 152 may be formed in contact with a first surface
of the piezoelectric layer 156, and a second electrode 154 may be
formed in contact with a second surface of the piezoelectric layer
156 that is opposite the first surface. According to an embodiment,
the piezoelectric sensor 150 is able to produce an electrical
signal (e.g., a voltage differential) when the piezoelectric layer
156 is compressed. The electrical signal is picked up by the first
electrode 152 and the second electrode 154 and delivered to a die
160 by one or more pads 140 and/or vias 142.
[0034] In order to provide a usable signal to noise ratio,
embodiments of the invention include a high performance
piezoelectric material for the piezoelectric layer 156. For
example, the high performance piezoelectric layer 156 may be lead
zirconate titanate (PZT), potassium sodium niobate (KNN), zinc
oxide (ZnO), or combinations thereof. High performance
piezoelectric materials such as these typically require a high
temperature anneal (e.g., greater than 500.degree. C.) in order to
attain the proper crystal structure to provide the piezoelectric
effect. As such, currently available piezoelectric actuators
require a substrate that is capable of withstanding high
temperatures (e.g., silicon). Low melting temperature substrates
described herein, such as stretchable substrates and dielectric
materials, typically cannot withstand such high temperatures.
However, embodiments of the present invention allow for a
piezoelectric layer 156 to be formed at much lower temperatures.
For example, instead of a high temperature anneal, embodiments
include depositing the piezoelectric layer 156 in an amorphous
phase and then using a pulsed laser to crystallize the
piezoelectric layer 156. For example, the piezoelectric layer 156
may be deposited with a sputtering process, an ink jetting process,
or the like. According to an embodiment, the pulsed laser annealing
process may use an excimer laser with an energy density between
approximately 10-100 mJ/cm.sup.2 and a pulsewidth between
approximately 10-50 nanoseconds. Utilizing such an annealing
process allows for the high performance piezoelectric layer 156 to
be formed without damaging the materials surrounding the
piezoelectric sensor 150.
[0035] According to an embodiment, the piezoelectric sensor 150 may
be utilized as a BCG sensor to monitor the acoustic waveform
produced by the heart of a user. Particularly, as the acoustic
waveform from a heartbeat passes the piezoelectric sensor 150, the
waveform compresses the piezoelectric layer 156. The compression of
the piezoelectric material 156 induces a voltage differential
across the piezoelectric layer 156, and the first electrode 152 and
the second electrode transfer the electrical signal to the die 160.
As such, the piezoelectric sensor 150 may be used to monitor the
heartrate of a user wearing the wearable system 100.
[0036] As described above, the use of BCG information in
conjunction with another heartrate monitoring technique (i.e., ECG
or PPG) allow for the blood-pressure to be calculated. In one
embodiment, an ECG sensor may also be integrated into the wearable
device 100 to provide the electrical waveform to the die 160 in
addition to the acoustic waveform detected by the piezoelectric
sensor 150. In an embodiment, the ECG sensor may include one or
more conductive pads 140 formed on the bottom surface of the
stretchable substrate 110. Accordingly, direct contact with the
skin may be made and the ECG signal may be sent to a die 160 on the
wearable system 100. Additional embodiments may include an ECG
signal that is obtained from a sensor that is remote to the
wearable system 100. For example, an ECG signal may be wirelessly
transmitted (e.g., Bluetooth, Wi-Fi, etc.) to the die 160 in the
wearable system 100 by a pacemaker that is external to the wearable
system 100. Additional embodiments may also include combing the BCG
signal of the piezoelectric sensor 150 with a signal from a PPG
sensor (not shown) in order to monitor blood-pressure. Furthermore,
some embodiments may include a wearable system 100 that includes a
PPG sensor, an ECG sensor, and a piezoelectric BCG sensor.
[0037] In an uncalibrated device, the signals obtained from two or
more of the piezoelectric sensor 150, and one or both of an ECG
sensor and a PPG sensor may be used to monitor changes in the
blood-pressure. Alternative embodiments may include a wearable
device 100 that can be calibrated. In a calibrated device the
signals obtained from two or more of the piezoelectric sensor 150,
and one or both of an ECG sensor and a PPG sensor may be used to
monitor the actual blood-pressure of a user of the wearable system
100.
[0038] Referring now to FIG. 2A, a cross-sectional illustration of
a wearable system 200 with a piezoelectric sensor 250 formed in a
stretchable portion 211 is shown, according to an embodiment of the
invention. The wearable system 200 may be substantially similar to
the wearable system 100, with the exception of the location of the
piezoelectric sensor 250. Moving the piezoelectric sensor 250
outside of the rigid portions 212 provides several advantages. One
advantage is that the size of the piezoelectric sensor 250 may be
increased since the piezoelectric sensor 250 does not need to be
within the footprint of a die 260. Increasing the size of the
piezoelectric sensor 250 increases the signal strength that may be
generated by a heartbeat. Accordingly, the signal to noise ratio
may be increased relative to a piezoelectric sensor that has a
smaller footprint. The improved signal to noise ratio may provide a
more reliable and accurate determination of the heartrate and/or
blood-pressure.
[0039] Additionally, positioning the piezoelectric sensor 250 in
the stretchable portion 211 allows for improved contact with the
skin (not shown) of a user of the wearable device 200. While the
piezoelectric sensor 250 may not be as stretchable as the
meandering traces 222, the piezoelectric sensor 250 may be bendable
and/or flexible. As such, the piezoelectric sensor 250 may be able
to conform to the surface of the skin better than when the
piezoelectric sensor is formed in a rigid portion 212. The improved
conformability with the skin of the user allows for improved
detection of the heartbeat, thereby providing an increased signal
to noise ratio.
[0040] Referring now to FIG. 2B, a cross-sectional illustration of
wearable device 200 is shown, according to an additional embodiment
of the invention. The wearable device 200 in FIG. 2B is
substantially similar to the wearable device 200 illustrated in
FIG. 2A, and further includes a stiffening mass 258 formed above
the piezoelectric sensor 250. Such an embodiment may be utilized
when the piezoelectric sensor 250 does not have the necessary
stiffness against the skin to allow for an adequate stress to
develop inside the piezoelectric layer 256 in order to generate a
readable electrical signal. According to an embodiment, the
stiffening mass 258 may be a high modulus material and/or a high
density material. For example, the stiffening mass 258 may be a
metallic material, (e.g., copper, stainless steel, etc.), a ceramic
material, or any other material that can provide the requisite
stiffness. Additional embodiments may omit the stiffening mass 258
and utilize a thicker second electrode 254. The increased thickness
of the second electrode 254 may provide an effect substantially
similar to the use of the stiffening mass 258. Furthermore, while a
stiffening mass 258 is illustrated as being used in conjunction
with the embodiment illustrated in FIG. 2A, it is to be appreciated
that a stiffening mass 258 may be used in conjunction with any
embodiments described herein in a substantially similar manner.
[0041] Referring now to FIG. 3A, a cross-sectional illustration of
a wearable device 300 is shown, according to an additional
embodiment of the invention. The wearable system 300 is
substantially similar to the wearable devices 200 described above,
with the exception that a plurality of piezoelectric sensors
350.sub.1-350.sub.n is arranged in a sensor array 351 in a
stretchable portion 311. According to an embodiment, the plurality
of piezoelectric sensors 350.sub.1-350.sub.n provide a larger total
sensing area that may provide an improved signal to noise
ratio.
[0042] Additionally, embodiments of the invention include
electrically coupling the individual piezoelectric sensors 350 with
meandering traces 322/324, as illustrated in the plan view shown in
FIG. 3B. Accordingly, a high signal to noise ratio may be obtained
while still maintaining the ability to stretch. Such an embodiment
may, therefore, provide improved contact with a user's skin.
[0043] Additionally, embodiments of the invention may include
forming the plurality of piezoelectric sensors 350 in a pattern
that matches the path of a blood vessel of a user. Such an
embodiment may allow for advanced cardio analysis. For example, a
plurality of piezoelectric sensors 350.sub.1-350.sub.n formed along
the length of a blood vessel may allow for the localized
distribution of the pressure wave of a user's blood flow to be
determined.
[0044] Referring now to FIGS. 4A-4I, a process flow for forming a
piezoelectric sensor in a wearable device in accordance with an
embodiment of the invention is shown. While a single wearable
device is illustrated in FIGS. 4A-4I, it is to be appreciated that
a plurality of wearable devices may be fabricated in parallel on
the same carrier substrate. For example, a plurality of wearable
devices may be fabricated at the panel level (e.g., 0.5 m.times.0.5
m) or the quarter-panel level. Accordingly, hundreds of wearable
devices may be processed in parallel, leading to compatibility with
high-volume manufacturing.
[0045] Referring now to FIG. 4A, pads 440, meandering traces 422,
and the first electrode 452 are formed over a carrier substrate
405. In an embodiment, a release layer 406 may also be formed over
the carrier substrate 405 to allow for easier removal of the
wearable device in subsequent processing operations.
[0046] Referring now to FIG. 4B, the piezoelectric layer 456 may be
formed over the first electrode 452. According to an embodiment,
the piezoelectric layer may be formed over the first electrode 452
with a selective deposition process, or a patterning process. In
order to provide a usable signal to noise ratio, embodiments of the
invention include a high performance piezoelectric material for the
piezoelectric layer 456. For example, the high performance
piezoelectric layer 456 may be PZT, KNN, ZnO, or combinations
thereof. High performance piezoelectric materials such as these
typically require a high temperature anneal (e.g., greater than
500.degree. C.) in order to attain the proper crystal structure to
provide the piezoelectric effect. As such, currently available
piezoelectric actuators require a substrate that is capable of
withstanding high temperatures (e.g., silicon). Low melting
temperature substrates described herein, such as stretchable
substrates and dielectric materials, typically cannot withstand
such high temperatures. However, embodiments of the present
invention allow for a piezoelectric layer 456 to be formed at much
lower temperatures. For example, instead of a high temperature
anneal, embodiments include depositing the piezoelectric layer 456
in an amorphous phase and then using a pulsed laser to crystallize
the piezoelectric layer 456. For example, the piezoelectric layer
456 may be deposited with a sputtering process, an ink jetting
process, or the like. According to an embodiment, the pulsed laser
annealing process may use an excimer laser with an energy density
between approximately 10-100 mJ/cm.sup.2 and a pulsewidth between
approximately 10-50 nanoseconds. Utilizing such an annealing
process allows for the high performance piezoelectric layer 456 to
be formed without damaging the surrounding layers on which the
piezoelectric sensor 450 is formed.
[0047] Referring now to FIG. 4C, a dielectric layer is deposited
and patterned to form the dielectric covering 424 over the
meandering traces 422 and the dielectric layer 444 over pads 440
and the first electrode 452. In an embodiment, the dielectric layer
may be patterned to provide openings for subsequent conductive
layers. The deposition and patterning of the dielectric layer may
include standard electronics packaging operations (e.g., blanket
deposition of a photo-imagable dielectric, followed by exposure,
developing, and curing of the photo-imagable dielectric).
[0048] Referring now to FIG. 4D, a seed layer 407 may be formed
over the exposed surfaces. The formation of the seed layer 407
allows for subsequent plating of conductive features and may be
performed with techniques and processes known to those with skill
in the electronics packaging arts. Thereafter, lithography for a
second metal layer may be implemented, as illustrated in FIG. 4E.
For example, the lithography may include standard processes and
materials, such as the deposition of a dry-film resist 485,
exposure of the dry-film resist 485, and developing of the dry-film
resist 485 to form openings 441 and 453 for forming the subsequent
metal layer.
[0049] Referring now to FIG. 4F, the subsequent metal layer is
formed. For example, the exposed portions of the seed layer 407 may
be used to selectively deposit conductive material with a plating
process, such as electroplating. As illustrated, the plating
process may be used to form vias 442, pads 440, and the second
electrode 454.
[0050] Subsequent to the plating process in FIG. 4F, embodiments of
the invention may include stripping the dry-film resist 485 and
removing the remaining portions of the seed layer 407, as
illustrated in FIG. 4G. For example, the dry-film resist 485 may be
removed with an ashing process and the seed layer 407 may be
removed with an etching process.
[0051] Referring now to FIG. 4H, embodiments of the invention may
include subsequent processing operations to form any additional
dielectric layers 444, conductive layers (e.g., conductive pads
440, vias 442, traces 422, etc.), and integration of needed dice
460.
[0052] Additionally, a stretchable substrate 410 may be deposited
over the electrical components. In an embodiment, the stretchable
substrate 410 may be formed with a pouring process. For example, a
precursor liquid may be poured over the carrier 405 and then
polymerized and cross-linked to form the stretchable substrate
410.
[0053] Referring now to FIG. 4I, the carrier 405 and the release
layer 406 may be removed after the formation of stretchable
substrate 410 is completed. By way of example, the carrier 405 may
be removed with a delamination process, an etching process, or any
other processes known in the art. Additionally, when a plurality of
wearable systems are formed in parallel, a dicing or other
singulation operation may be implemented to separate each device,
in accordance with embodiments of the invention.
[0054] FIG. 5 illustrates a computing device 500 in accordance with
one implementation of the invention. The computing device 500
houses a board 502. The board 502 may include a number of
components, including but not limited to a processor 504 and at
least one communication chip 506. The processor 504 is physically
and electrically coupled to the board 502. In some implementations
the at least one communication chip 506 is also physically and
electrically coupled to the board 502. In further implementations,
the communication chip 506 is part of the processor 504.
[0055] Depending on its applications, computing device 500 may
include other components that may or may not be physically and
electrically coupled to the board 502. These other components
include, but are not limited to, volatile memory (e.g., DRAM),
non-volatile memory (e.g., ROM), flash memory, a graphics
processor, a digital signal processor, a crypto processor, a
chipset, an antenna, a display, a touchscreen display, a
touchscreen controller, a battery, an audio codec, a video codec, a
power amplifier, a global positioning system (GPS) device, a
compass, an accelerometer, a gyroscope, a speaker, a camera, and a
mass storage device (such as hard disk drive, compact disk (CD),
digital versatile disk (DVD), and so forth).
[0056] The communication chip 506 enables wireless communications
for the transfer of data to and from the computing device 500. The
term "wireless" and its derivatives may be used to describe
circuits, devices, systems, methods, techniques, communications
channels, etc., that may communicate data through the use of
modulated electromagnetic radiation through a non-solid medium. The
term does not imply that the associated devices do not contain any
wires, although in some embodiments they might not. The
communication chip 506 may implement any of a number of wireless
standards or protocols, including but not limited to Wi-Fi (IEEE
802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term
evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS,
CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any
other wireless protocols that are designated as 3G, 4G, 5G, and
beyond. The computing device 500 may include a plurality of
communication chips 506. For instance, a first communication chip
506 may be dedicated to shorter range wireless communications such
as Wi-Fi and Bluetooth and a second communication chip 506 may be
dedicated to longer range wireless communications such as GPS,
EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
[0057] The processor 504 of the computing device 500 includes an
integrated circuit die packaged within the processor 504. In some
implementations of the invention, the integrated circuit die of the
processor may be packaged on a stretchable substrate that includes
a piezoelectric sensor for determining heartrate, in accordance
with implementations of the invention. The term "processor" may
refer to any device or portion of a device that processes
electronic data from registers and/or memory to transform that
electronic data into other electronic data that may be stored in
registers and/or memory.
[0058] The communication chip 506 also includes an integrated
circuit die packaged within the communication chip 506. In
accordance with another implementation of the invention, the
integrated circuit die of the communication chip may be packaged on
a stretchable substrate that includes a piezoelectric sensor for
determining heartrate, in accordance with implementations of the
invention.
[0059] The above description of illustrated implementations of the
invention, including what is described in the Abstract, is not
intended to be exhaustive or to limit the invention to the precise
forms disclosed. While specific implementations of, and examples
for, the invention are described herein for illustrative purposes,
various equivalent modifications are possible within the scope of
the invention, as those skilled in the relevant art will
recognize.
[0060] These modifications may be made to the invention in light of
the above detailed description. The terms used in the following
claims should not be construed to limit the invention to the
specific implementations disclosed in the specification and the
claims. Rather, the scope of the invention is to be determined
entirely by the following claims, which are to be construed in
accordance with established doctrines of claim interpretation.
[0061] Embodiments of the invention include a wearable device,
comprising: a piezoelectric sensor embedded within a stretchable
substrate, wherein the piezoelectric sensor comprises: a
piezoelectric layer; a first electrode formed in contact with a
first surface of the piezoelectric layer; and a second electrode
formed in contact with a second surface of the piezoelectric layer
that is opposite to the first surface.
[0062] Additional embodiments of the invention include a wearable
device, wherein the wearable device comprises a rigid portion and a
stretchable portion.
[0063] Additional embodiments of the invention include a wearable
device, wherein the rigid portion comprises a semiconductor die,
and wherein the stretchable portion comprises meandering
traces.
[0064] Additional embodiments of the invention include a wearable
device, wherein the piezoelectric sensor is formed in the rigid
portion, and wherein the piezoelectric sensor is formed within the
footprint of the semiconductor die.
[0065] Additional embodiments of the invention include a wearable
device, wherein the piezoelectric sensor is formed in the
stretchable portion.
[0066] Additional embodiments of the invention include a wearable
device, wherein the piezoelectric sensor is electrically coupled to
the semiconductor die by one or more meandering traces.
[0067] Additional embodiments of the invention include a wearable
device, further comprising a stiffening mass formed above the
piezoelectric sensor.
[0068] Additional embodiments of the invention include a wearable
device, further comprising a plurality of piezoelectric sensors
formed in the stretchable portion.
[0069] Additional embodiments of the invention include a wearable
device, wherein the plurality of piezoelectric sensors are
electrically coupled to each other by meandering traces.
[0070] Additional embodiments of the invention include a wearable
device, wherein the plurality of piezoelectric sensors are arranged
in a pattern similar to the shape of a blood vessel.
[0071] Additional embodiments of the invention include a wearable
device, further comprising one or more stiffening masses formed
above the plurality of piezoelectric sensors.
[0072] Additional embodiments of the invention include a wearable
device, further comprising an electrocardiogram sensor.
[0073] Additional embodiments of the invention include a wearable
device, wherein the semiconductor die is configured to receive
signals from the electrocardiogram sensor and the piezoelectric
sensor and generate a blood-pressure measurement.
[0074] Additional embodiments of the invention include a wearable
device, wherein the blood-pressure measurement is an absolute
blood-pressure measurement.
[0075] Embodiments of the invention include a method of forming a
piezoelectric sensor in a wearable device, comprising: forming a
first electrode on a carrier substrate; forming a piezoelectric
layer on the first electrode; forming a second electrode over the
piezoelectric layer; forming a stretchable substrate over the
carrier substrate, wherein the stretchable substrate encases the
first electrode, the piezoelectric layer, and the second electrode;
and removing the stretchable substrate from the carrier
substrate.
[0076] Additional embodiments of the invention include a method of
forming a piezoelectric sensor in a wearable device, wherein
forming the piezoelectric layer, comprises: depositing the
piezoelectric layer over the first electrode, wherein the
piezo-electric layer is an amorphous layer; and crystallizing the
piezoelectric layer with a pulsed laser anneal.
[0077] Additional embodiments of the invention include a method of
forming a piezoelectric sensor in a wearable device, wherein the
piezoelectric layer is deposited with a sputtering or ink-jetting
process.
[0078] Additional embodiments of the invention include a method of
forming a piezoelectric sensor in a wearable device, wherein the
pulsed laser anneal is performed with an Excimer laser with an
energy density in the range of approximately 10-100 mJ/cm.sup.2 and
pulse width in the range of approximately 10-50 nanoseconds.
[0079] Additional embodiments of the invention include a method of
forming a piezoelectric sensor in a wearable device, wherein the
piezoelectric layer is lead zirconate titanate (PZT), potassium
sodium niobate (KNN), or zinc oxide (ZnO).
[0080] Additional embodiments of the invention include a method of
forming a piezoelectric sensor in a wearable device, wherein a
plurality of wearable devices are formed on a single carrier
substrate.
[0081] Embodiments of the invention include a wearable
blood-pressure monitor, comprising: a stretchable substrate; a
semiconductor die embedded in the stretchable substrate; an
electrocardiogram sensor electrically coupled to the semiconductor
die; and a ballistocardiograph sensor embedded within the
stretchable substrate and electrically coupled to the semiconductor
die, wherein the ballistocardiograph sensor is a piezoelectric
sensor that comprises: a piezoelectric layer; a first electrode
formed in contact with a first surface of the piezoelectric layer;
and a second electrode formed in contact with a second surface of
the piezoelectric layer that is opposite to the first surface.
[0082] Additional embodiments of the invention include a wearable
blood-pressure monitor, wherein the semiconductor die is configured
to receive signals from the electrocardiogram sensor and the
ballistocardiograph sensor and generate a blood-pressure
measurement.
[0083] Additional embodiments of the invention include a wearable
blood-pressure monitor, wherein the piezoelectric sensor is formed
within the footprint of the semiconductor die.
[0084] Additional embodiments of the invention include a wearable
blood-pressure monitor, wherein the piezoelectric sensor is not
formed within the footprint of the semiconductor die, and wherein
the piezoelectric sensor is coupled to the semiconductor die by one
or more meandering traces.
[0085] Additional embodiments of the invention include a wearable
blood-pressure monitor, further comprising a plurality of
piezoelectric sensors, wherein the plurality of piezoelectric
sensors are electrically coupled to each other by meandering
traces, and wherein the plurality of piezoelectric sensors are
arranged in a pattern similar to the shape of a blood vessel
* * * * *